i am trying to make a peltier powered mini fridge and i am having some trouble getting it to get to the temperatures i want.
First of all, some info. I am using a Cooler Master T4 as the cooler for the peltier's hot side. The problem is that the contact surface of the fan's heatsink is smaller than the peltier's, so i get really hot edges. That is why i bought a 1mm thick copper sheet to put between the peltier and the fan.
I am powering it all with an old 350W computer power supply. It should be enough.
I first bought a 12706 peltier element and tried the setup. Since i don't have an accurate thermometer, i meassured the performance by measuring the current that the peltier drawed and checked if the cold side was cold enough to freeze water drops.
If i don't put the copper sheet, and just add some thermal paste, i get around 3.8 A and the cool side is cold enough to freeze water. My concern with this setup is that the edges of the peltier(that are not in contact with the heatsink) are really hot and i am afraid to damage the element.
If i add the copper and put some thermal paste in both sides, i get 2.5A, that is much less than the previous setup. This way i can't get it cold enough.
Then i bought two more peltier modules, the 12710 this time, and some thermal pad to repalce the thermal paste for something more durable.
This time i get around 5.4A when using just the thermal paste and 5.2A with just the thermal pad. The edges are still really hot, but at least i am able to freeze water. It doesn't seem to be any colder that the 12706 though.
However i am noticing that the wires in the peltier get hot, so i am suspecting that they are limiting the amount of current. Maybe that is why i don't get best performance with the 12710.
So, what am i doing wrong? I know for example that the copper sheet should be as flat as possible, maybe that is why i don't get proper thermal conduction.
Should the 12710 get colder than the 12706? Because if not i am wasting a lot of power for nothing.
Will my peltier get damaged if i let it run with hot edges?